Snow White Auto Wah build doesn't sound right.

[nguitar12]

Hi everyone so I recent built a Snow White Auto Wah according to the following schematic and layout:

schematic here  ,  layout here

I finished the build but it just doens't sound right. Yes I can get a wah sound only when I turn the Sensitive knob all the way down and I have to strum it VERY HARD in order to make it wah. I cannot even get a wah sound when I play a single note.

The first question is I am not sure whether the direction of the 78L05 as shown on the layout is correct or not. It seem that the Vin and Vout is reversed but I am not sure because I saw Everyone's bulid using this layout is installing 78L05 like this.

For example this one   and   this one

But for me if I installing 78L05 in this direction it will become very hot and I cannot get a deserved voltage for BC550 . So I hope someone can help confirm this.

The second thing that I would like to confirm is whether the non polarized capacitor I used is correct or not. I am using :

CBB(104) .................. for CX , C10 (100n)
CBB(683) .................. for C2 (68n)
CBB(223) .................  for C1 , C5 , C6 (22n)
CBB(224) .................  for C3 (220n)
CBB(822) .................  for C4 (8n2)

Here is the substituted parts I use:

1. Replace R26(7.9K) into 7.8k    ........................................  I don't know if it will cause any problem
2. Replace VR4 (C1M) into A1M by wiring it backward ..........  As suggested by some member here before. I can hear the pot is doing the job
3. Replace TL074 into LM324 .............................................. I saw some other SWAW schmatic is using this IC and they have the same pin configuration.

If someone need a voltage on certain point I can measure for you. I really want to get this pedal work. This is my second bulid on this. My first try is completely fail using this layout . I think this try is nearly success so I really someone here can help my on this.

Finally, my work here:

[alexradium]

the first layout by rapidriot works like a charm,perfect at first try for me.
Your board is poorly made,try to clean with alcohol all around the copper traces and be sure there are no shorts between them.
Check out all the voltages on the chips and trannies,that's where you can understand what is missing.

[nguitar12]

the first layout by rapidriot works like a charm,perfect at first try for me.
Your board is poorly made,try to clean with alcohol all around the copper traces and be sure there are no shorts between them.
Check out all the voltages on the chips and trannies,that's where you can understand what is missing.

Thanks Alex, I am sure there are no shorts between the trace I spent almost one hours to check it.
Can you please confirm my question on the 78l05 chip?

Actually my pedal is working but I think there may be some problem on the sensitive circuit. I had to strum it very hard to generate enough dynamic. Here is the pin voltage voltage for all IC:

Battery: 9.04v

[alexradium]

position on the 78l05 is correct in your build.

[Kipper4]

Is the transistor in red shorted?

[Mark Hammer]

This is one of those instances where I would recommend a) not using quite so much solder (although it's still only about 60% of what MXR would often use on some of the early products!), and b) taking a used toothbrush and some methyl hydrate or other flux dissolver, and removing as much of the excess flux on the solder side as possible.

It's not so much a comment on the aesthetics, as identifying what has been, in my own experience (and I imagine that of others), an obstacle to being able to easily spot solder bridges, cracks, etc.  Sometimes just cleaning up the copper side will make something previously overlooked jump out at you.  Sometimes.

[nguitar12]

Is the transistor in red shorted?

Yes I later on find that pin 3 is shorted to left path but it make no different after I fixed the problem

[nguitar12]

position on the 78l05 is correct in your build.

Thanks. So this one   and   this one is installing the 78l05 wrongly? Why they can get their pedal working? Is there are another type of 78l05 that is having another pin out?

[nguitar12]

This is one of those instances where I would recommend a) not using quite so much solder (although it's still only about 60% of what MXR would often use on some of the early products!), and b) taking a used toothbrush and some methyl hydrate or other flux dissolver, and removing as much of the excess flux on the solder side as possible.

It's not so much a comment on the aesthetics, as identifying what has been, in my own experience (and I imagine that of others), an obstacle to being able to easily spot solder bridges, cracks, etc.  Sometimes just cleaning up the copper side will make something previously overlooked jump out at you.  Sometimes.

Thanks I started to think that my pedal is actually working just the sensitively circuit is having some problem. I later on bypassed R18 to it more sensitive to the dynamic. Now the pedal is usable when the sensitive knob is turned before 12 o'clock.  but I still cannot get a wah sound knob is turned over this position. I don't unstanding why I have to do this as the circuit is not supposed to be like this.

[chemosis]

yes i have this same issue were my sensitivity seems weak. like the filter dosent open up all the way so it sounds dark and somewhat like a %^&*ed wah. i tried mpsa 18 i tried bc550c and bc 550b and my pcb is from fuzzdog and really solid

[chemosis]

my sensitivity knob does work but its not sensitive enough. i guess ill try increasing it